Prime Guard Carb & Choke Cleaner is a powerful and fast acting carb & choke cleaner. Its formula is designed to power through harmful carbon, gum, and varnish deposits, cleans carburettors, automatic chokes, PCV valves and lines, and manifold heat control valves. With the engine cold and off, remove the air filter and then spray the carb & choke cleaner on the exterior surface of the carburettor and linkage. Spray ends of choke valve while opening and closing manually.